CHEVY LOW IDLE THEN DIES

ya I have an 03 chevy silverado lifted 6 inchs it has a 4.8 v8 with around 172573 miles and it been like this for a while I took it in they had no idea y it dose it but it low idles then it dies when I trun park or change gars I have a progarmer on it but when I take it off it dose the same thing if you could help that would be great

I also have an 03 chevy silverado with a similar and had the same problem and got it fixed. The problem from what I understood is there is a carbon buildup around the air intake and doesnt allow it to " breath" properly. Mine would flutter but if I went around corners the engine would die from the load of the power steering and no gas. It would be ok if I went around the corner with my foot slightly on the gas. You could probably do it yourself and not have the dealer do it.